What is the origin of the word ZAX?

WWF accepts it as a valid word. I can only find in defined in one dictionary, Merriam Webster. It says it’s like a hatchet that is used by roofers.
It is not listed in the Oxford dictionary, or the Cambridge.
I can’t find the origins of it any where. I checked Etymology.com. It isn’t listed.

I’m having a debate with a friend over the validity of the word, ZAX, and the word ZAXE, which WWF does not accept. She keeps insisting that they’re both valid words. If AX is a valid word, and AXE is a valid word, then ZAXE is a valid word since they both mean a type of ax.
I mean, I’ll take any word that lets me play a Z and X in the same word, but I can’t find any more information on the word.

Is some random invention of the age of playing online word games?